About Optics & Photonics TopicsOSA Publishing developed the Optics and Photonics Topics to help organize its diverse content more accurately by topic area. This topic browser contains over 2400 terms and is organized in a three-level hierarchy. Read more.

Topics can be refined further in the search results. The Topic facet will reveal the high-level topics associated with the articles returned in the search results.

Abstract

We experimentally demonstrate tunable radiation from a periodic array of plasmonic nanoscatterers, tailored to convert surface plasmon polaritons into directive leaky modes. Extending our previous studies on efficient directional beaming based on leaky-wave radiation from periodic gratings driven by a subwavelength slit, we experimentally show dynamic beam sweeping by tuning the directional leaky-wave mechanism in real-time. Two alternative tuning mechanisms, wavelength- and index-mediated beam sweeping, are employed to modify the relative phase of scattered light at each grating edge and provide the required modification of the radiation angle.

Figures (6)

Schematic of a tunable directional optical antenna: a subwavelength slit with a left-side array of periodic gratings, consisting of corrugations in a plasmonic screen. Note that εD,εM,andεSUBindicate the relative permittivity of surrounding medium, metal, and supporting substrate (BK7), respectively. Directive radiation at a specific angleθcan be achieved by a proper choice of surrounding mediumεDand wavelengthλof operation; and its directivity can be further enhanced by optimizing illumination angleϕ.

Measured far-field radiation patterns from the proposed configuration with (a) various index matching fluids and (b) various wavelengths of operation. TM polarized light with spectral FWHM of 10 nm was used throughout experiments. Note that each recorded radiation pattern is normalized to its peak intensity.

Measured radiation patterns of the configuration shown in Fig. 1 for normal illumination (black curve, open circle) and tilted illumination (blue curve, filled box) for enhanced directive radiation. Index matching fluid with a refractive index of 1.34 was introduced and TM polarized light at 630 nm was used to excite the slit. Measured FWHM for normal incidence was 36.0°; whereas the case for tilted illumination was 19.1°.